Digital maps are displayed and are used in a wide variety of devices, including car navigation systems, hand-held GPS units, mobile phones, and many websites. Moreover, digital map databases may contain a wealth of information such as satellite images, roads, street photographs taken from the ground level, specific information for a business, three dimensional computer models, etc. Digital maps that incorporate three dimensional computer models may, for example, include buildings, structures, and natural geographic features such as trees, as three dimensional objects. Digital maps may further include terrain topography as a three dimensional raised relief map. However, the information contained within a digital map, as stored in a map database, is frequently updated and changed by digital map developers, three dimensional computer modeling users, digital map users, and computer systems that automatically aggregate information from the Internet. These frequent map updates and changes are especially prevalent with the large number of three dimensional modeling users. With so many modeling users uploading models to the modeling digital map, the likelihood of a user uploading an incorrect or inaccurate model remains high. In response to the possibility of an incorrectly updated model, other modeling users may wish to be notified of any model update. However, when map information is updated for a particular location, such as a three dimensional building update, no propagating means exists to notify an interested user of the map information update.
One conventional technique for determining a change to information stored in a map database for a particular location involves manually examining the information for that particular location via a website or a digital map service. Although this simple inspection is an easy method of determining whether information for one location has been updated, it quickly becomes time consuming and difficult to monitor map information changes occurring for a multitude of locations within a geographical area, such as an entire downtown area.
Another conventional technique for determining when a change is made to information stored in a map database includes subscribing to a text subscription list or email listserv for businesses or commercial entities, such as restaurants, located within a particular geographical area. In this case, the listserv for the particular restaurant or other business entity automatically propagates a notification to the user when any information update about the business or commercial entity occurs, such as a change of menu, a change of opening and closing hours, etc. While the user is able to obtain the new information relatively quickly, this technique is still time consuming and is difficult to use to monitor information changes occurring for a multitude of restaurants or other business entities within a particular geographical area, as a separate subscription must be set up for each business or commercial entity offering the service. Moreover, this technique is limited to obtaining information updates directly from the businesses or commercial entities that offer a subscribing service, which is generally less than all of the businesses or commercial entities within a particular geographical area. Moreover, it is not possible to use this technique to obtain updates being applied to general information stored in map databases, such as changes made to road data, changes in satellite images, etc.